import  pandas as pd
df=pd.DataFrame({'商品':['苹果','香蕉','梨'],'单价(元)':[5,5,4],'销量（kg)':[100,None,None],'库存(kg)':[50,None,None,70]})
print('原始数据: \n',df)
print('删除包含缺失值的行: \n',df.dropna)
print('删除包含缺失值的列: \n',df.dropna(axis=1))
print('删除少于3个非缺失值的行: \n',df.dropna(thresh=3))
print('删除库存列包含缺失值的行: \n',df.dropna(subset=['库存（kg)']))